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How a piston corer works
After being lowered on a wire from the side of a ship, the piston corer approaches the seafloor preceded by the small gravity corer.
Upon contact, the tripping arm "opens," sending the piston corer on a fast fall to the bottom.
As the piston corer penetrates the seafloor, the piston inside stops at the sediment surface. The action of the piston creates a pressure differential at the top of the sediment column. This allows the soft material to enter the core liner without disruption.
Within seconds, the process is complete. Crew on the ship then haul the wire in until the corer is free of the seafloor. (Illustration by Fritz Heide, WHOI)